The present invention relates to direct current (DC) power systems, and more specifically, to a system that implements silicon carbide (SiC) metal on oxide field effect transistors (MOSFET) and silicon controlled rectifiers (SCR) for DC generation, power management, and DC power distribution.
Power generating systems such as those that can be implemented in military ground vehicles employ a permanent magnet generator (PMG) coupled with an active rectifier, followed by the power management and distribution (PMAD) unit. Conventional PMAD units utilize electromechanical contactors for high current circuits. These conventional electromechanical power switches have very low voltage drop and losses, but suffer from several limitations that are addressed with solid state power controllers (SSPCs). Electromechanical switches have a very slow response time requiring many tens of milliseconds to switch. This speed limitation results in excessive let-through energy into a fault, compromising the overall PMAD function. The speed limitation also presents significant challenges to advanced bidirectional bus architectures that require rapid PMAD fault response to ensure uninterrupted power to the loads.
Replacing electromechanical contactors with SSPCs for currents above 50 ADC present significant challenges. The electromechanical contactor is very efficient due to its low on-state resistance. Currently, a silicon carbide (SiC) power MOSFET is implemented in many solid state contactor applications, due to the ability to achieve a lower on-resistance and a higher current rating by paralleling several devices. A typical trip curve requires an increase of current capability of the solid state contactor up to 1000%. Increasing the number of parallel SiC MOSFETs helps to increase current capability of the solid state contactor but increases SSPC complexity, cost and size. As such, there is a need to improve current capability of the solid state contactor with a minimum impact on its cost and size.